Portable electric spot welding apparatus



June 30, 1953 Q H. WATSQN PORTABLE ELECTRIC SPOT WELDING APPARATUS 3 Sheets-Sheet l Filed DeC. 3. 1949 am n N5 R O T N E V m ATTORNEYS June 30, 1953 C, H WATSON 2,644,067

PORTABLE ELECTRIC SPOT WELDING APPARATUS Filed Deo. 3, 1949 T 5 Sheets-Shea?l 2 ATTOR NEYS June 30, 1953 C. H. WATSON PORTABLE ELECTRIC SPOT WELDING APPARATUS Filed Deo. T5. 1949 5 Sheets-Sheek 3 6 a. Z8a Z8 Z7 ZZ 3l FYI 37 F 6 Q J F '1 .1.3 1E| Q 43 v) 240 y 3220 46 oo /80 INVENTOR 2 /o cow/wmv H. w/mso/v /40 Qt q /ZO BY W 0 z 4 6 a /o /z /4/6 ATTORNEYS Patented June 30, 1953 PORTABLE ELECTRIC SPOT WELDING APPARATUS Coleman H. Watson, Birmingham, Ala., assignor of sixty per cent to Aaron Sachs, Bessemer.

, Ala.

Application December 3, 1949, ScrialNo. 130.9251

7 Claims. 1

My present invention relates to electric welding apparatus, and more particularly to electric resistance spot Welders.

The primary object of my invention is the provision of an entirely portable electric spot welder in which the welding head or gun is light in weight, compact and eicient, and which shall be capable of welding pieces of material together by applying the electrodes of the gun to a common side of one of the pieces to be welded.

Another object is to provide apparatus of the characted designated which shall be capable of spot welding a sheet of material to another body of metallic material of infinite thickness, or which, with equal facility may be used to weld together a pair of thin sheets by the use of a suit'- able backing bar of conducting material.

Another major object of my invention is to provide a spot Welder operable from a source of alternating current and in which the welding current transformer is carried in the welding head or gun, whereby the large inductive losses of voltage in the welding circuit which are present in prior art apparatus is reduced substantially to zero, one reason for this reduction in losses being the fact that I am enabled to reduce considerably the distance betweenv the transformer secondary connection, namely the electrode circuit, and the work.

A further object is to provide a self contained welding transformer. housing and electrode holder for making spot welds in which the transformer is provided with a hollow cylindrical core formed of a continuous sheet of a high permeability silicon iron having superior magnetic qualities existing therein only in the direction in which the sheet was rolled in the manufacture thereof, together with a multiple turn secondary which supplies the electrodes with current, thus providing a portable spot Welder which is light in weight, in which the overall size of the gun is reduced to a minimum and which may be manufactured at a fraction of the cost of the present opposed electrode, non-portable type of apparatus of generally similar welding capacity.

A further object is to provide a welding transformer in which the secondary thereof comprises a relatively heavy, divided and twisted bar or rod of conducting material, the endsV of each section thereof being alternately electrically connected to the divided housing, whereby the currentA in said secondary flows in series therethroughto the welding electrodes, thus raising the voltage of the welding current and increasing the efliciency and welding capacity of the apparatus over the capacity and eliiciency of the same if a single turn secondary was employed, and without increasing the weight or size thereof to any material extent.

Another object is to provide an entirely portable spot Welder in which the energizing switch for welding transformer control circuits is carried on the gun or head and closeable by downward movement of a suitably spring biased handle, together with a timing circuit for controlling the duration of flow of welding current, whereby the necessary mechanical pressure of the electrodes against the work is obtained and the weld made by the operator pressing downwardly on the handle, thus reducing the actual making of the weld to the simple manual operation of placing the electrodes at the desired place on the work and pressing down on the operating handle, assuring the making of good welds by even unskilled operators. 1

Further and more general objects are to provide a fully portable spot Welder which shall produce high quality welds, which shall be low in initial cost, economical, safe and trouble free in operation; in which the entire apparatus including a substantially constructed carrying case therefor shall weigh in the neighborhood of 50 pounds including about 20 feet of cable; and in which such apparatus has the capacity of making welds between metallic sheets, the sheet contacted by the electrodes being up to 16 gauge, and in which the other of which may be of innite thickness.

Apparatus illustrating the features of my invention isshown in the accompanying drawings forming a part of this application in which:

Fig. 1 is a somewhat diagrammatic perspective view, partly broken away showing my complete apparatus with the gun removed from the carrying case and in place on a pair of metallic members to be welded;

Fig. 2 is a plan view ofthe welding gun;

Fig- 3 is a bottom view thereof;

Fig. 4 is an end elevational View of the gun;

Fig. 5 is an enlarged side elevational view partly broken away and in section to show the internal construction of the gun;

Fig. 6 is a detail sectional view taken generally along line VI-VI of' Fig.l 5

Fig. 7 is a. View of the divided and'twisted secondary of the transformer removed from the remainder of the apparatus;

Fig.l 8 is an end' view of the secondary;

Figs. 9 to 11 inclusive are detail sectional views taken on the4 respective'lines indicated on Fig. 7;

Fig. 12 is a somewhat diagrammatic wiring diagrain showingthe complete circuit for the Welding gun and control circuit therefor; and,

Fie. 13 is a graph illustrating the charging volt voltage-arnperage relation of the welding transformer to be described more in detail herein.

Referring now to the drawings for a better un derstanding oi"- iny invention, and more partticularly to Fig. 1, my improved apparatus comprises generally two units. First, the saine comprises the weldinghead or gun lll constructed and arranged as will be hereinafter more deinitely set forth. Second, there is provided a suitable carn rying case Il. The case l! has a storage corfu partrnent it therein for receiving the gun proper, and immediately surrounding compartment i3 is a space ifi for receiving the pair oi cables. ln the opposite end of the carrying case there ,is ample space for housing the control and mechanism and portions of the circuits therefor. Electricity is supplied to the unit through the input oat-le and is supplied to the gun through the cable l1. The carrying il he prom vided with a suitable hinged cover U3 and a lo in the form of a hasp le.

As shown incre particularly in elusive the welding gun lll coinpr generally cylindrical cody portion. body is preferably formed of an upper bstantially se;"i-cylindri-1 cal section ill and lower end sections and also substantially semi-cylindrical. .lach of the sections ill, and 23 is provded at each d with heads 2t, 2t and respectively. The heads preferably are cast integrally with the reniaining portions of the several As shown more clearly in the detailed drawing, the cent edges of the upper and lower sections, oe-th of the longitudinal portions the are spaced apart and preferably have strips 2li and Ella of insulating material interposed tween. The lower sections 122 and are held spaced apart and insulated. from each other by means of a band 2e of insulating material. The band may he secured to the sections il? and by means or" hat head rivets 3i or lthe like. L wise, the adjacent inner edges of the sections and 23 are insulated, preferably hy a strip 32 o insulating material, The sections 2l, and 23 are 'held assembled by means of discs 33 of sulating material and screws ill passing throng the discs and into the heads Ell, 2li and El.

On the underside of each of the sections t2 and 23, and preferably formed, integrally therewith are hos-ses 3Q and 3l. The bosses are provided with tapering op nings 353 in which are disposed to be pressed the tapering upper ends fili and 4| of a pair of electrodes 42 and GB. The electrodes may be cast members, and as is usual for `such devices the lower or shank portion thereof tapers downwardly and terminates in a spherical point 45.

'From the description so given it will he seen that with the upper and lower sections oi' the gun body assembled there iF provided a space on the inside thereof. lin this space l. place the improved form of welding transformer now to he described.

The transformer core el preferably comprises a continuous sheet oi a high permeability silicon iron which, in the process of its manufacture, has been so rolled and heat treated and otherwise handled that the individual crystals thereof line up with cube edges essentially parallel to each other and to the direction of rolling. A suitable material of this kind is sold by the Westinghouse Electric Corporation, Sharon, Pennsylvania, un-

end Wall 2l' or" the lower housing half 23.

der the trade name Hipersih and the specific type of the saine which I prefer to use is riesighated in booklet B 3701, issued by that cornpany in July 1946, and designated under the grade designation oi C 97 (29 Guage) The core fil thus comprises a sheet of such material which has been rolled during manufacture longln tudinally or" its length and is then wound in spiral form to the shape of a cylinder. After rolling the sheet to spiral form thereby to form the core lll', l' insulate the exterior, ends interior thereof with a suitable material such as resin impregnated cotton fabric 48Q The primary of the transformer comprises a continuous length of insulated wire ii-l passed through the central opening or the core, aro. the ends anden the outside thereof. I erably so design the entire apparatus that the wire of the vrequired. size, when laid on the core, provides a single layer on the exterior surface of the core and a double layer in the bore or centrally disposed opening thereof. The lil and 52 of the primary winding are connected to a pair of wires 53 and El@ in the cable Il. These wires are connected to the source oi current through the control and timing mechanisms circuits in the manner later to be described.

The secondary of the transformer preferably comprises a pair of elongated copper, aluminum, or aluminum alloy members and 5l, serni-cir cular in 'transverse section and insulated from each other by a strip of insulating material 5S. lin forming the secondary of the transformer l :Find it convenient to use a rod of material of high electrical conductivity such as copper of a diameter 'to i'lt into the here oi the core after the prir Ay winding is laid thereon, and using of aoout the thickness ci a hand hack. saw clade to saw the rod down the middle from end to end. new lay the strip of insulatiiig material lil-l between the halves so formed and place the halves together. Holding one end of the sawerl rod in a vise, I engage the other endv with suitable clamping tool and twist 'the rod bodily .es seen in Figs, and '5l to ll, inclusive, this results in two turn secondary, and the slots or lines oi' division between the halves thereof are horizontally disposed at each end or second and El I d' l'n the ends of the sections 55 ll and tap holes 59. I now assemble `the transformer .into the housing, further insug lating the primary winding 49 from the housing by means of suitable insulating material 6l as indicated in Figs. 5 and 5. The secondary is o held in place, and the ends thereof are clcctriu cally connected to the heads 2t, 2t and 2l by means of screws 62 passing through the discs of insulating material, the heads, and thence .into the tapped holes 5t.

Considering Fig. 5 it will be 'that one end of the half 5S of the secondary .is electrically connected to one end wall 2li oi the upper hous-M ing section 2l. The other end oi the half due to the fact that the secondary is twisted, electrically connected by the screws S2 to the in like manner, the end of the half 51 adjacent the end of the half 15 connected to the upper housing, is connected by the screws t2 to the end wall 25 of the lower housing section 22. Due to the twisting of the secondary, the opposite end of the half 5l is connected by the screws 62 to the opposite head 24 of the upper housing section 2|. Thus, the direct and inductive electrical circuits between the electrodes may be traced as follows: Commencing at electrode 42 the path of current is through the end wall 2t of the lower housing section 22, to one end of the secondary half 57, and thence to the opposite end wall 2li of the upper housing section 2|. Electrode 43 is similarly connected to the associated end of the secondary half 5B by the associated screws Se through the end wall 2l, while the opposite end of the half 51 is in turn connected to the opposite end wall 24 of the upper housing section 2|. The voltage of the current induced in the respective halves of the second ary thus is additive, since there are two turn-s in the secondary and the total voltage available for welding is equal to twice the voltage in each of the turns of the secondary. Since the rines of force cut by the two halves are substantially identical in number, the Voltage in each turn of the secondary is the same for all practical purposes.

The energizing, timing and control apparatus and circuits which I prefer to employ with the apparatus so far described will now be set forth in detail. .As shown more clearly in Figs. 2 and 5 I form on top of the upper section 2| a pair of longitudinally spaced bosses E3 and S4. The bosses are connected along their sides by inn tegrally formed ribs 66 and 67. Upstanding from the bosses G3 and 54 are pairs of spaced ears 5t and te. In the pairs of earsi and E9 are aligned, vertically elongated openings I and l2.

Disposed lto slide vertically between the ears and toward and from the bosses t3 and te is an operating handle 'i3 preferably formed of non conducting,r material. Passing through the ends of the handle and the pairs of ears are pins 'h1 and i6. The pins are of a size to nt sidably in the elongated openings, and may be retained in place by means of Cotter pins 'I'I passing therethrough.

The bosses t3 and t4 and the adjacent ends of the underside of the handle 73 are provided with recesses 'it and i9, respectively. the recesses are compression springs SI. The springs 8| are designed to require a considerable downward force on the handle I3 prior to permitting relative downward movement of the handley for a purpose later to be described.

Mounted between the ribs 66 and |51, beneath the central portion of the handle I3 is a single pole double throw switch S2. The switch has an operating .handle 33 disposed in position to be closed to its other or normally open position upon downward movement of the handle. The cable Il is secured to the welding head I by means of a plate 84 held to the side of the rib te by means of screws 85.

Referring now to Fig. l2 of the drawing, I show diagrammatically a wiring diagram for the complete apparatus. In Fig. l2, the dotted line i'l encloses those portions of the apparatus which are in the gun I proper, while Jche dotted line @8 encloses those portions which are in the car rying case II. As shown, the cable Il contains individually insulated wires. Of these wires, wire 5t, leading 'from the end 52 of the welding transformer primary 49, leads to the case I and thence connects directly as` shown in Fig. 12 to the powe supply line L2. The Wire 53 connected to the welding transformer primary i9 at 5| leads to the slidewire connection 89 of a variable voltage auto transformer A. One terminal of the auto transformer winding connects through a wire 9| to the line L2. The other terminal of the auto transformer winding is connected by.

Fitting within` a wire 32 to the movable contact 93 of a line relay or contactor, indicated generally by the letter B. The fixed contact point 94 of the relay B is connected to the line LI through a wire 96. One lead of the coil of the relay B connects through a wire ETI to the supply line L2, and the other lead thereof is connected through a wire 98 to the movable contact Se of a second relay C. The fixed contact point Il of the relay C is connected by a wire |02 to the line Ll One vterminal of the coil of the relay C is connected by a wire |33 to the normally open contact point it of the switch 82. The opposite terminal of the coil of the relay C is connected by a wire'ltt to a wire IIBI in turn connected at each end to one end of a fixed resistance |08 and to one end of the resistance element of a rheostat Idil. The slide wire |I| of the rheostat Ide is connected by a wire II2 to the wire |533. The end of the fixed resistance |08 opposite the wire ltd is connected by a wire I|3 to a wire I I4 con nected at one end to the plate of a rectifier IIS and at its other end to one plate of a condenser I I l. The opposite plate of the condenser is connected by a wire H3 which leads to the blade of the switch e2. The normally closed contact point Ile of the switch t2 is connected to the end 52'01" the welding transformer primary its by means of a wire |2I.

As usual, the third wire L3 in the cable Iii is a ground wire and is connected in any suitable manner to the carrying case I| for safety Durposes. The fth wire |22 in the cable I'l is connected by a screw |23 to the upper housing section 2| and is then grounded to the case through a choke coil I2, also carried in the case.

From the foregoing the method of constructing my improved spot Welder, the method of its operation and the advantages thereof may now be readily explained and understood. From the arrangement of the divided housing and its relation with respect to 'the twisted secondary it will be apparent that the housing itself forms a part of the electrical circuit for the welding operation, the lower end sections being the terminals of the secondary circuits. The secondary of the welding transformer is a part of the welding head and the area enclosed within the welding loop is reduced to a minimum. For this reason the electromotive force in the secondary terminals of the transformer need not be more than a total of 3 volts, namely, a total of one and onehalf volt for each turn ci the secondary. I thus not only eliminate the large inductive losses in the prior art apparatus wherein it is attempted to carry the high current from the secondary of a transformer to the electrodes, but also reduce to the minimum the tendency of the electrodes to burn holes in thin metal. As has been before stated, the conipactness of the construction makes the entire welding gun extremely light in weight. "With the it connected to a suitable source of voltage, for instance a source of 220 volt, 60 cycle alternating current it will be apparent that the switch 82 is closed to the position to connect the movable blade thereof to the contact point lli?, it being remembered that the operating handle it is upwardly biased by means of the springs 5|. 'Under these conditions the condenser II'I is charged with a given quantity of current depending upon its capacity, since the current therefor is derived from the lines LI and L2 through the rectifier IIB. As the operating handle 73 is moved downwardly the movable blade of the switch closes against contact lll,

energizing the coil of the relay C. rllhis closes the contact points il@ and lill of the relay C,

in turn energizing the coil of the relay B, causing the contact points 93 and e4 thereof to close. 5 From an inspection oi the wiring diagram it will be apparent that this energizes the primary winding it of the welding transformer with energy irorn the auto transformer A. As soon as the charge on the condenser has dissipated itself the circuit to 'the coil of relay C is broken, and this breaks the circuit to the coil of relay thus deenergiaing the primary winding llt, The quantity of the charge of the condenser Ill is determined by the line voltage. However, due to the effect of the resistanees lila and it the t' ne or energisation oi the winding 49 is modin ivd determined by the setting of the rhecstat lili?. The voltage impressed upon the winding t@ deter lined by the setting of the slide wire i, of the auto transformer. These controls are indicated respectively in Fig. l of the drawing by the corresponding numerals lill? and Bil and also by the dials a d scales marked time and heat, respectively. will be noted that once the transformer primary del is energized, the saine remains energized until the condenser discharge Thus, regardless of the position of the handle enerigzation time depends entirely upon the time that it takes the condenser lil to dis-- its current. Therefore, by suitably ad current to as high as 1/4 of a second or longer it able. in. actual. practice, I have found that a lured resistance oi 250 ohms and a variable ren siste-noe oi i000 olnns when using a loo reid. condenser i il, is ample to provide the time range necessary for the usual welding purposes. luikewise, 'the rectifier HG may be ci' the simple, dry disc type, no vacuum tubes or the like being required. practice I prefer to employ a selenium disc type renti-her.

iin making the weld with rny improved apparatos t: e tor merely places the electrodes fill and at the place desired, having set auto transformer for the voltage required and 'the rheostat for the time required, presses downwardly on the handle It will be seen that due to the pre-loading of the springs ill there is provided at the point of contact of electrodes with the top sheet to be welded a pressure which is equal both to the weight of the welding gun itself and to the increase rel1 quired to compress the springs Si.

Referring to lig. 13 of the drawing l show a ph ol the primary voltage oi the transformer 'win g de plotted against the Charging current produced thereby. lt will be seen that the knee ci the curve is considerably higher than would be the il the core were made of ordinary laminated iron. The voltage in the secondary at .Mii volts :in the primary was found to be apxiinately 1.670 volts per turn. This chart was ade iroin a Welder in which the total weight ci tie welding gun was pounds. The dimens sions of the core, which was made from C 9i' (22l gauge Upersil, were inches long, 3.625 in major diameter, and with a central opening of 1.375 inches in diameter. The secondary was formed of a copper rod 1.25 inches in diameter and o inches long, and the primary win g consisted oi 145 turns of No. 'l5 single cotton, enameled, magnet copper wire. With a welding apparatus thus constructed I 75 have successfully welded sheets of steel oi'from a iew thousandths inch thick up to .0626 inch thick, and have welded such sheets onto other sheets oi varying thicknesses. l'n this connection l desire to point out also that my improved apparatus is capable of making welds between sheets in which the lowerrnost one or the underside of the uppermost one is rusty, or otherwise scaled or oxidized. For instance, the ordinary niill scale on the lower surface of the upper sheet or on the upper surface of the lower sheet apparently does not abject either the welding time or the duality of the nnalweld produced. When welding thin sheets to each other, I place a low resistance l) (Fig. 1) or" copper or the like behind the lower sheet to act as a conductor to help carry the current. This is necessary if the sheets being welded are so thin as to create an excessive voltage drop, as will be apparent to those skilled in the art.

While l have shown the secondary as being a two turn secondary, it will be apparent that by dividing a rod of copper or the like into three segments and twisting the saine only and in provicing a housing divided into four one could es easily produce a three turn Or, other nufphers of turns or a sinoould he provided if esirable, it tod. that the number of housing sections secondary. gie

plus one. actual practice secondary e -loweve, I have found as a niatter of 'oerience that the two turn is the best for the general e ci welding for which spot Welders are suited. lroin the foreg 'ng will be apparent that I have devised an improved spot welding apparatus. ention has particular utility in connection wim welding iron roofing or siding to steel frame 'buildings the like, in the making of woven wire fence and. the like, for general sheet welding purposes in and around fabricating shops, and in any other installation in which an efficient, portable, low cost spot Welder is desired. lt will also be seen that the current in the primary winding oi rny improved apparatus not excessive, and that the saine may used by plugging into the usual outlet provided in shops and the like. I preferably design the apparatus for use on 229 volt circuits, but it will be apparent to those skilled in l the art that the device could be made to operate on il@ volts, fir-li) volts, or any other voltage by properly calculating the requirements of the transfo-finer accordance with known formulae. Further, in the event it is desired to produce only one weld at time instead of one under each of the electrodes iii and 4S I can accomplish this by replacing one oi the electrodes with a relatively wide surfaced electrode in. which event welding takes place only at the smaller or pointed electrode. Further, :for the purpose ci welding round rods or other odd special tips can be provided, and off tips likewise can be used for special applications. have been able to reduce the Weight of proved welding head or gun from the pounds mentioned above for the one made oi' copper to lii pounds and l0 ounces for a gun of equal capacity made oi aluminum or certain aluminum alloys.

While have shown iny invention in but one forni, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of vari ous changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed there- 9 uponas are speciiically set forth in the appended claims.

What I claim is:

l. In an electric resistance spot weiden-a welding gun embodying a shell type housingdivided into three sections one ci which entends from end to end o1 the housing and the other two or which extend partially from end ,to end thereof, said sections being electrically insulated from each other, a welding transformer in said housing ernu bodying a hollow core and a primary winding on said core, a two conductor secondary winding for said transformer located in said core each oi which has one end electrically connected to continuously extending housing section and the opposite end thereof connected to one oi the other housing sections, electrodes electrically connected to said other housing sections, and means to supn ply the primary with alternating current.

2. A Welder as defined in claim 1 in which the secondary winding comprises a pair of conducting members substantially semi-circular in transverse section and insulated. from each other, .said sections being twisted 180 throughout the length thereof.

3. In a welding gun, a housing having therein a welding transformer embodying a cylindrical core with a primary winding thereon, a plurality of conductors located within the cylindrical core and forming a secondary winding for the transH former, said housing being divided into a pair of terminal sections and an intermediate section, the sum of said sections being equal in number to the number of conductors in the secondary plus one and said sections being electrically insulated from each other, the conductors or said secondary winding being electrically connected in series to said housing sections whereby current produced in the secondary flows in series through the conductors of the secondary winding and through the intermediate housing section and the terminal sections, electrodes electrically connected to the terminal housing sections, and means including a source of E. M. to energize the primary winding.

4. A welding transformer having a core formed of a rectangular sheet oi silicon iron wound into cylindrical. shape with a centrally disposed opening therethrough, said sheet of material having individual crystals of the iron lined up with cube edges essentially parallel to each other and paralilel to the direction of the length of the sheet, a primary winding comprising a plurality of turns of wire laid on the outer surface of the core, across the ends and through the opening thereof, a two turn secondary winding for the transformer comH prising two solid substantially semi-cylindrical conductors of substantially equal cross sectional area assembled to form a generally cylindrical two conductor secondari7 portion located in the core, said conductors being twisted throughout their length. substantially 180, the diameter of said assembled two conductor secondary portion being slightly less than the diameter or the central opening of the core with said primary winding in place therein, means electrically insulating the semi-cylindrical conductors of the secondary winding from each other, and means electrically connecting together an opposite end of each of said semi-cylindrical conductors thereby comn pleting said two=turn secondary winding.

5. Apparatus as donned in claim l in which each of said housing sections embodies an end wall substantially semi-circular as Viewed in end elevation and in which said secondary comprises I-10 a pair of members substantially semi-circular as viewed in end elevation and of a length to extend from end wall to end wall of the housing.

6. In an electric weldcr, a metallic housing comprising an upper semi-cylindrical section, generally semi-circular end walls formed integrally with the upper section, a lower liousinU section comprising two semi-cylindrical sections each equal in length to approximately one half the length of the upper sectionya generally semin circular end wall formed integrally with and at one end of each lower section, means holding said housing sections assembled and electrically insulated 'from each other to denne a centrally open cylindrical shell with the end walls of each lower housing section lying substantially in the same plane with the adjacent end walls of the upper housing section, a transformer in said shell comprising a primary winding and a core having a longitudinally disposed cylindrical opening therethrough, a secondary winding for the transformer in the form of a solid rod oi electrical conducting material divided longitudinally into a pair of semi-cylindrical sections equal in length to substantially the distance between the inner surfaces of the end walls of the assembled housing sections, said sections of the secondary being twisted throughout the length thereof, means elec-l trically connecting the oppositely disposed. ends of each of said sections of the secondary to the end walls of the upper housing section and the other ends thereof to the adjacent end walls of the lower housing sections, a pair of welding electrodes carried by the lower housing sections, and means including a source of E. M. F. to energize the primary winding whereby current induced in the secondary winding flows in series therethrough and through said housing sections.

7. In a welding gun, a shell-like housing assembly comprising an upper generally semi-cylindrical. elongated. section, a lower generally semicylindrical section divided transversely of the length thereof into two sections, means holding all of the housing sections assembled and out ci' electrical contact with each other, a transformer comprising a cylindrical core in the housing with the longitudinal axis oi the opening therethrough substantially coincident with the longitudinal axis of the housing, a primary winding wrapped about and through said core, a two conductor secondary in the opening of said core in the form or" an elon-- gated metallic rod fitting snugly in the core openu ing and divided along the longitudinal axis thereof into a pair of elongated semi-cylindrical sections, insulating material between the conductors of said secondary, means electrically connecting tho oppositely disposed ends of each of said secondary conductors to the adjacent end of the upper housing section, means electrically con necting theY other oppositely disposed ends oi said secondary conductors to the adjacent sections oi' the lower housing, electrodes electrically connected to the lower housing sections, and means to energize the primary winding.

COLEMAN H. WATSON.

References Cited in the file of this patent UNITED STATES PATENTS Number .Name Date 1,086,041 Gravell Feb. 3, i914 1,247,741 Taylor' Nov. 27, 1917 1,779,365 Von Henke Oct. 2l, 1930 (Other references on following page) Number 1I UNITED STATES PATENTS Name Date Le Van et al July 12, 1932 Stausbury et al Dec. 27, 1932 Groven Mar. 12, 1935 5 Martn Dec. 8` 1936 Martin Dec. 8, 1936 Bohn Apr, 4, 1939 Eckman Nov. 7, 1939 Flinn Feb. 18,1941 19 Number Number Name Date Martn Jan. 19112 Platz Oct. 27, 1912 Mesch et a1 Feb. 22, 19441 DEntremont Feb. 24, 1.9416

FOREIGN PATENTS Country Date France June 28, 19413 

